The invention relates to a hairdryer comprising an axial fan and a cage-shaped electrically energized resistor for heating the air blown through the apparatus by the axial fan.
Most conventional hair dryers comprise a heating element composed of resistance wires or ribbons and a motor-driven fan blowing air in axial direction through the heating element. In some of these hair dryers the fan motor is placed close to or inside the heating element and, in order to prevent its overheating, the motor is surrounded by a shield of mica or another heat-resistant material.
U.S. Pat. No. 4,328,818 discloses a hair dryer of a design completely departing from the former conventional construction. Herein the hair dryer comprises a cage-shaped resistor and a motor-driven axial fan enclosed in an oblong casing of circular cross section. The fan sucks in air through circumferential inlet openings and blows it through the cage from its outside periphery into its interior, and from there through outlet slots into a cylindrical brush attached to the front of the casing.
The fan is of much larger diameter than the outer diameter of the resistor cage, and the portion of the casing surrounding the fan and most of the resistor cage is enlarged in bulbous shape, defining an annular air duct of gradually decreasing cross section around the case periphery. The shape of the duct results in an air flow of relatively low axial velocity and causes its diversion through the cage blades in substantially uniform distribution over the entire circumference of the heater.
The cage-shaped resistor contains a plurality of parallel, axially extending thin blades which are curved and inclined in respect of the peripheral surface of the cage to effect maximal heating efficiency while straightening the air flow which emerges in spiral direction from the axial fan impeller before entering the heater.
The electric motor, the fan, and the resistor are arranged in line, the motor being positioned in the space of the casing which is perforated by the inlet openings, the resistor cage at the other end just in front of the air outlet openings leading to the cylindrical brush, while the fan impeller is mounted on the motor shaft and located between the motor and the cage.
Although the total longitudinal extent of the three components is relatively large, they fit readily into the oblong casing and the coaxial handle portion; however, in a conventional, pistol-shaped hair dryer composed of a substantially cylindrical main casing portion with a downwardly extending handle portion, it would require a rather long main portion causing the hair dryer to be heavy and unwieldy. This is a drawback which to obviate is one of the objects of the present invention.
Another drawback of the hair dryer of the aforementioned patent, U.S. Pat. No. 4,328,818, lies in the fact that the power settings of the resistor cannot be adjusted, since all vanes of the cage are connected in series. The air temperature is only controllable by suitably changing the motor revolutions, in a known manner, whereby more or less air is blown by the fan through the resistor and is accordingly heated to a lower or higher temperature, respectively.
The present invention has, therefore, the main object of providing a hair dryer of a more compact build and lighter weight than the existing, conventional hair dryers, while employing air moving and heating means substantially identical with those described in my previous patent but in a different manner of arrangement designed to obtain this object.
It is an additional object, not obtained with my previous hair dryer in U.S. Pat. No. 4,328,818, to provide means for heating the cage to at least two different settings of temperature to be selected by the user.
And it is a further object to provide a hair dryer with a low flow resistance in order to obtain the required heating effect and air flow by means of a relatively small-diameter fan impeller and an accordingly small-wattage motor.